Wall covering is adhered to walls, ceilings or other surfaces, by the use of an adhesive. Decorative sheet material such as wall coverings are formed typically of paper, plastic, metal foil, or fabric material having a pattern or design printed or embossed on the front surface, with the other surface, or back, being coated with the adhesive. Other types of wall coverings include those having a plastic decorative surface and a backing of woven or non-woven fabric or paper.
Some wall coverings adhere to walls by virtue of wet glue, cement or the like (typically known as "wallpaper paste") applied to the wall or wall covering before hanging. Typically, the backing or back surface is adapted to be coated by the user with the aforementioned wallpaper paste to secure the wall covering to a surface. However, consumers dislike the inconvenience of mixing and applying the paste. Other wall coverings are prepasted. The paste of prepasted wall coverings is wetted before hanging the wall covering. However, prepasted wall coverings need a water pan, and this can be messy. Pressure sensitive adhesives (PSA) may be employed in place of the paste. PSAs have the advantage that they avoid employing wet paste. However, PSA do not allow the wall covering to be easily repositioned and aligned. It would be advantageous to provide an easily repositionable and alignable wall covering which employs PSA.
Generally, conventional wall coverings, which employ paste, permit the wall covering to be shifted or adjusted, after application to a surface, to a limited degree until the adhesive paste cures, or dries. In contrast to paste, PSAs rely on high initial tack and/or quick set-up reaction, or cure time for prompt or instant adhesion. Thus, PSAs with sufficiently high tack to hold a wall covering in place make it very difficult to apply a wallpaper to a wall and then reposition the wallpaper, as occurs for example, while matching up patterns from one wallpaper strip to the next. Although suitable pressure sensitive adhesives have in the past been applied to wall coverings, attempts to reposition those same wall coverings generally have not met with success. Typically, wall coverings having PSA have fallen from the walls to which they were applied shortly after such application due to poor permanent adhesion. Also, the wall covering cannot be slid and repositioned while in contact with the wall due to adhesive tack. Various spacer means have been used to separate the adhesive from the wall in attempting to introduce some slip until a permanent adhesion is attained. However, the outline of such spacer means shows through the decorative face of the wall covering. It is also difficult to manufacture wall covering by placing spacer means having the proper thickness or position over an adhesive coating.
The following references are illustrative of the prior art.
U.S. Pat. No. 3,301,741, Henrickson et al discloses a self-adhering wall covering comprising: a substrate, such as paper; a pressure sensitive adhesive; and a separation means secured to or a part of the back side of the substrate. The spacer means are of a uniformly pebbly contour of raised adhesive protrusions on the back separated by intervening adhesive planar areas wherein the tips of the protrusions are of a friable non-adhesive material which crumble into particles upon the application of pressure to the substrate. Also, the tips of the adhesive projections can be coated with a non-adhesive coating.
U.S. Pat. No. 5,141,790, Calhoun et al discloses a repositionable PSA sheet wherein the PSA has clumps thereon with non-adherent material distributed on the clumps.